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The Journal of Bone and Joint Surgery 80:925-6 (1998)
© 1998 The Journal of Bone and Joint Surgery, Inc.

Correspondence

Correspondence

Joseph Bernstein, M.S., M.D., Robert L. Barrack, M.D., Michael W. Wolfe, M.D., Alexander J. Bertot, M.D., Douglas A. Waldman, M.D., Matko Milicic, M.D. and Leann Myers, Ph.D.

TO THE EDITOR:

"Resurfacing of the Patella in Total Knee Arthroplasty. A Prospective, Randomized, Double-Blind Study" (79-A: 1121–1131, Aug. 1997), by Barrack et al., while excellent, would have been better had the authors reported the statistical power3 of their study. Power quantitates the likelihood of a so-called type-II error—that is, concluding that two groups are similar when they are indeed different.

Examination of the comparative data shows that the group that had patellar resurfacing actually gained more motion and had greater improvements in the pain, function, and overall scores. (It may be said that these were clinically unimportant differences, and they may be, but that is not a statistical argument.) As the probability was more than 0.05 that these distinctions owed more to chance than to true differences—that is, the differences were not significant—Barrack et al. concluded that the outcomes in the two groups were similar. This may be a . . . [Full Text of this Article]


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